The present invention relates to a rotary compressor in which transporting elements slide with the free ends thereof along an endless cam curve to draw in and compress a fluid medium, especially a gaseous fluid medium, during rotation of the impeller. In rotary compressors of the aforementioned kind there is only a single working space provided which has the disadvantage that the compression- and mass-forces are not balanced. Furthermore, due to the direct communication of inlet and outlet passages with the single working space, as for instance shown in the U.S. Pat. No. 1,192,978, oil is always contained in the compressed fluid medium, which is undesirable.